Supply system for pulsating-torque motors.



R. E. HELLMUND.' SUPPLY SYSTEM FOR PULSATING TORQUE MOTORS.

APPLICATION FILED HAY20.19I6.

Patented Aug. 27,, 1918.

4 SHEETSSHEEI' 1.

.9 -Ezaux.

AAAAAAAA 11111111111.

"WWW" LARA IIIIIII [a aux.

AAAARAAH III/Ill wvvvvv AAAAAAAA IIIIII AAAAAAAAA IIIIIIII INVENTOR Fade/g fie/lmuna.

ATTORNEY R. E. HELLMUNDL SUPPLY SYSTEM FOR PULSATING TORQUE MOTORS.

Patented Au 27, 1918.

APPLICATION FILED MAY 20. I916.

4 SHEEIS-QSHEEI 2.

I I I I 'IIW d M m 0/ T/ in d m ATTORNEY R. E. HELLMUND.

SUPPLY SYSTEM FOR PULSAIING TORQUE MOTORS.

APPLICATION HLED MAY 20;!916.

- Patented Aug. 27, 191&

44 a" II E fim Ely/Z.

WITNESSES 1 INVENTOR Q C? Edda/f5. He/Mu/na.

R, E. HELLMUND.

SUPPLY SYSIEM FOR PULSATING TORQUE MOTORS.

APPLICATION FILED MAY 20, )9I6.

Patented Aug. 27, 1918.

4 SHEETSSHEET 4.

V V V INVENTOR fiaaa/ff/ffi/mund.

WITNESSES 1 ATTORNEY rATENT orFIcE.

BUDOLF It ELLNUND, or PITTSBURGH, PENNSYLVANIA, ASSIGNOR 'ro WESTING- nousn ELECTRIC AND NUrAc'rUm G COMPANY, A coaronA'rroN or rENNsYL- VANIA.

To all whom it may concern Be it known that I, RUDoLF E. HELLMUND, a subject of the Emperor of Germany, and a resident of Pittsburgh, in the county of Alleghenv and State of Pennsylvania, have invented a new and useful Improvement in Supply Systems for Pulsating Torque Motors, of which the following is a specification.

My invention relates to systems of current supply for pulsating-torque motors, hav ng relation particularly to motors of the singlephase, commutator type, and it has for its object to provide means whereby a load designated may be adjusted for desirable .a sequence chart illustrating operation. I e In the accompanying drawing,'Figure is a diagrammatic view of two alternatingcurrent motors of the single-phase, crossfield, commutator t ne.'t0 'ether with their attendant supply circuits, illustrating one form of my invention; Fig. 2 is a vector diagram illustrating the relatlon of the current and voltage vectors in the system of Fig. 1; Figs. 3, 1, 10 and 11 are diagrammatic views of modifications of the system shown in Fig. 1; Figs. 5, 6, 7 and 8 are simplified diagrammatic views illustrating the development of 4; Fig. 9 is the connections shown in Fig.

the order of operation ofthe switches of Fig. 4 in order to produce Figs. 5 to 8, inclusive; Figs. 12, 13 and 15 1 f ,ing my invention and applied to a larger z f n umber of motors,

four; Figs. 14 and the acceleration indicated in are diagrammatic views of systems embodysuch, for example, as

operation in the systemsof Figs. 13 and 15;

of a single-phase system is pulsating in; char- ,necessarily pulsating.

substantially uniform in character.

I 16 are sequence charts H setting forth the preferred order of switch and Figs. 17 and 18 are detail views illus- SUPPLY SYSTEM FOR PULSATING-TORQUE Morons.

, Specification of Letters Patent. vPatented Aug, 2'7, 1918, Application filed May 20, 1916. Serial No. 98,786. I I

acter so. that: the torque developed by a slngle-phase alternating-current motor is .The efiects of said pulsating torque may be greatly reduced by the fly-wheel action, of the rotor and of othermoving parts but, nevertheless, there still remains a perceptible vibratory action which may have a harmful effect upon the operation of a railway vehicle. By my invention,I mechanically couple two or more -motors of the character indicated to a single load shaft and I' then provide means whereby the electromotive forces supplie d to said motors are caused to differ perceptibly in phase, whereby the torques of the different motors" maintain a distinct phase displacement from each other and the resultant torque s'uppiled to said load is accordingly Theo retically, inapplying my invention to two motors, it would be necessary to maintain a phase relation of substantially 90 between the two motor torques in order to obtain a; substantially uniform resultant torque but in practice, I find that a much smaller phase divergence than that indicated produces a suffibiently beneficial effect upon the operation. -The phase displacement between the electromotive forces supplied to different motors may be provided by a phase converter of the rotary type associated with a single-phase supply source.

a more nearly uniform torque supplied to a driving axle by the mechanical storage and release of energy obtained by inserting a resilient connection between each rotor and the axle. A

Referring to the drawing for a more detailed understanding of my invention, I show two motors of the single-phase, crossfield, commutator type at 1 and 2 in Fig. v 1. The motor 1 is provided with an armature 3, an exciting field winding 4, and an inducing-field winding 5 and, in like manner, the motor 2 1s provided with an armature 6, an exciting-field windin 7 and with an inducing-field winding 8. nergy for the operation of themotors 1 and 2 is derived from any suitable source, such, for example, as the secondary winding 9 of a transformer 10. 'While I have shown the transformer 10 as of .,the double-winding type, it may if desired,be an auto-transformer and be-energized by connect on between a trolley and ground, as is usual in ra lway Work, or by any other desired means. The motors 1 and v2 are connected in series relation across the supply winding 9 in accordance with the well known doubly-fed system, the cross-field windings 5 and 8 being connected respectively between the outer terminals of the supply winding 9 and suitable adjustable intermediate tap connections 11 and 12. A phase converter 13 of the rotary type has, its primary winding 14 connected across the supply windlng 9 and has its secondary winding 15 connected between substantlally the mid point of the supply winding 9 and a point 16 between the two motors 1 and 2. The rotor of the phase converter 13 is preferably provided with a squirrel cage winding 17 and with an exciting winding 18 which may be energized from a suitable direct-current source 19 through the usual slip rings. The armatures 3 and 6 are mounted on the same shaft 20 and resilient couplings 21-21, such, for example, as are shown in'Fig. 2 of U. S. patent to Priest 508,634, November 14, 1893, are preferably inserted therebetween for torque equalization.

Having thus described the arrangement of a system embodying my invention, the operation is as follows: The motors 1 and 2 are started and accelerated in any desired manner, and the machines 13 and 19 are also started and operated by any desired means, the specific instrumentality employed for this purpose forming no part of the present invention. The system thus being in operation, the voltages E and E impressed upon the two cross-field windings 5 and 8 may be represented by corresponding vec tors in Fig. 2. In like manner, the transformer voltage impressed upon the armature 3 and main-field winding at may be indicated by a vector 6 and that impressed upon the armature 6 and main field winding 7 by a vector 0 The voltage generated in,

the secondary winding 15 of the phase converter is substantially 90 out of phase with the electromotive force of the source 9 and may be indicated by a vector E. The resultant voltage upon the armaturev 3 and the main field winding 4 is indicated by a vector E and that impressed upon the armature 6 able phase difference between the resultant voltages E and E impressed upon the two motors and there is accordingly a phase difference between the pulsating torques thereof which is sufficient to produce a substantially uniform torque in the shaft 20. The capacity of the phase converter is equal to the product EI, whereas the total motor capacity is proportional to (E -PE 2aux+ 2) A) It ls-therefore posslble to produce a marked difference in the phase of the currents I and I with a phase converter capacity of only a small percentage of the main motor capacity. If the phase converteris utilized at the same time for driving auxiliary apparatus, such as air blowers and compressors, it entails but small additional expense over the customary locomotive equipment.

The adjustment of the direct-current excitation of the rotor of the phase converter 13 from the source 19 produces substantially no effect upon the phase conversion but may be caused to produce leading current for supply to the source 9 to neutralize the lagging current caused by the leakage flux, etc., in the motors 1 and 2.

Another advantage of the structure shown is that the small phase difference indicated between the auxiliary and armature voltages in each machine is beneficial to the commutation, causing the electromotive force produced by the rotation of the short circuited armature conductors undergoing commutation in the cross field to more nearly neutralize the joint effects of transformer and reactance electromotive forcestherein.

The objectionable effects of pulsating motor torque are much more noticeable at starting than during full-speed operation and, furthermore, the commutation problem is in general more diflicult at starting than during the latter stages of motor acceleration. For both of these reasons, it may be advisable to maintain the phase converter in circuit only during the starting steps, eliminatm'g the same during full-speed operation and thus permitting the use of a still smaller phase converter to produce a given phase-.

shifting effect. I

In the system "of Fig. 1, I have shown both motors as provided with main endwith general are as shown in Fig. 1 with the exception that a smgle cross 'field winding 22 is mounted to act upon both armatures. The

specific details of a twin motor embodying this construction, form no part of this invention but are separately shown and claimed in my copending application, Serial No. 76,152, filed February 4, 1916, and in a copending application of Rudolf E. Hellmund and Ralph E. Ferris, Serial No. 75,932, filed February 3, 1916, and assigned to the Westinghouse Electric & Manufacturing Company. Neither of said applica-' tions, however, disclose the use of a phase converter for producing phase displacement in the applied voltages and torques of the two elements of the twin-motor combination.

The motors of a system embodying my invention may be started and accelerated in any of the well known manners indicated inan article by R. E. Hellmund and J. V. Dobson, entitled "The single-phase commutator motor appearing on page 112 et seq. of the Electric Journal for March 1916, but I preferably start said motors as repulsion machines, with the armatures short circuited through resistance members, and thereafter accelerate them as doubly-fed motors, as indicated in Figs. 4 toi..=,9, inclusive. As the specific method of acceleration forms no part of the present invention, the same will be described but briefly. At the outset, the two motors are connected for repulsion operation, with the resistors inserted in the armature short circuits, (Fig. 5), intermediate taps being then established (Fig. 6),,

the repulsion connections removed (Fig. 7) and the armature voltages raised (Fig. 8).

, Fig. 10 shows the application of my invention to motors in which the main field windings are energized by the difference between the armature and cross field currents rather than by being energized by the armature current.

A phase-displacingjefl'ect similar tothat produced by a phase converter may be produced by an inductive winding, with the disadvantage, however, that lagging powerfactor correction is not possible. A system embodying this modification of my invention is shown in'Fig. 11, Two motors 1 and 2 are connected to derive energy from a supply winding 9, and said motors are of different capacity, the motor'l being larger than the motor 2. An inductive winding 41 is inserted in a connection from a point between the two motors to anintermediate point in the source, and the excess of load current of the motor 1 over that of the motor 2 fl WS th rethrough, Thus, the supseries 'plycircuit, of the 1 large motor 1 more highly inductive than that'of the small mo 1 tor 2 and the current therein therefore lags a greater amount, producing the desired,

phase displacement between the torques of the two motors. I

It is usual to supply electrical propelled vehicles, such, for example, as cars and locomotives, with four main motors. and I show an installation of this type embodying my invention in Fig. 12. Fourmotors, or rather two twin motors, of the single-phase, cross-field, commutator type are designated,

respectively, as 42, 43, 44 and 45.. 'The' motors 42 and 44 are mounted on one shaft and the motors 43 and45' are mounted on another. An intermediate connection to the source 9'i'ncludes an inductive device 41.for

phase conversion, as in the system of Fig. 11. The armature windings of, the motors 42 and 43 are connected inparallel to each other between the intermediate tap 11' and the lower end of the reactor 21. The armature of the motor 44 is connected between i an intermediate tap 12 and the lower end of the reactor 41, 'whereas the armature of the motor 45 is connected, between the intermediate tap 12 and the upper end of the reactor device 41, the exciting-field windings of the respective motors being connected in with their associated armatures. Thus, the power factors of the various armature circuits differ, and there is a phase difference between the armature currents of the armatures 42, 44 and 43 and 45, respectively, resulting in the production of sub stantially uniform torque in the two shafts.

Figs. 13 and 14 indicate a preferred mode of acceleration to be employed on locomotives embodying two or more pairs of twin motors. The system is of the general character indicated in Fig. 12, with the exception that a rotaryphase converter isem- F ployed for torque displacement rather than the reactancefdevice of Fig. 12. As indicated in the sequence chartof Fig. 14, the motors'are all started as repulsion motors and are subsequently changed over for doubly-fed acceleration, with a rising armature impressed voltage derived from an adjustable intermediate tap.

Figs. 15, 16, 17 and l8 relate to a similar system, with the exception that the motors are started in a doub-ly-fediconnection and the main fields are weakened by means of shunting inductance coils 66 and 67 in order to'reduce the transformer action of the heavy starting current flowing in the main field windings upon the short circuit'ed armature coils undergoing commutation. The two impedance'coils 66 and 67 arepreferably wound upon the same magnetic core, as shown in Figs. 17 andlS, for the purpose of q liz g he oad between the different single-phase,

motors, and said magnetic 'cores are preferably provided with incomplete magnetic circu1ts,-as shown, in order to increase the leakage flux and, therefore the inductive effect of the windings 66 and 67.

cross-field, commutator type, of a resilient mechanical coupling between the motors thereof, and means for maintainlng a phase difference between the electromotive forces applied to the armature windings of the two motors.

3. The combination with a source of single-phase, alternating-current, of two single-phase, alternating-current motors connected in series relation across a portion thereof, a connection from a point between said motors to an intermediate point in said source, and phase-displacing energy-storing and restoring means in said connection.

4. The combination with a source of single-phase, alternating current, of two, single-phase, alternating current motors connected in series relation across a portion thereof, a mechanical coupling between the rotors thereof, a connection from a point between said motors to an intermediate point in said source, and phase-displacing energy-storing and restoring means in said connection.

5. The combination with a source of single-phase, alternating current, of two alternating current motors connected in series relation across a portion thereof, a resilient mechanical couphn between the rotors thereof, a connection rom a point between said motors to an intermediate point in said source, and means for generating an alternatin electromotive force in said connection di ering in phase fromthe electromotive force of the main source.

6. The combination with a source of single-phase, alternating current, of two singlephase, alternating-current motors of the commutator type connected in series relation across a ortion thereof, a resilient mechanical coup ing between the rotors thereof, a connection from a point between said mo-. tors to an intermediate point insaid source, and means for generating an alternatin electromotive force in said connection di fering in phase from the electromotive force of the main source.

'7. The combination with a source of alternating current, of two alternating-current motors connected in series relation across a portion thereof, mechanical coupling means between the rotors of said motors, a connection from a oint between said motors and an intermediate point in said source, and a dynamo-electric phase-converter arranged to produce an electromotive force in said connection of like frequency to the electromotive force of the source but differing therefrom in phase.

8. The combination with a source of alternating current, of two alternating-current motors connected in series relation across a portion thereof, resilient mechanical coupling means between the rotors of said motors, a connection from a point between said motors and an intermedlate point in said source, and'a phase converter arranged to produce anelcctromotive force in said connection of like frequency to the electromotive force of the source but differing therefrom in phase.

9. The combination with a source of alternating current, of two alternating-current motors connected in series relation across a portion thereof, mechanical coupling means between the rotors of said motors, a conneo tion from a point between said motors and an intermediate point in said source, and a phase-converter having its primary winding connected to said source and having its secondary winding inserted in said connection, whereby an electromotive force is induced in said intermediate connection of like frequency to the electromotive force of said source but differing therefrom in phase.

10. The combination with a source of alternating current, of two alternating-current motors connected in series relation across a portion thereof, resilient mechanical coupling means between the rotors of said motors, a connectionfrom a point between said motors and an intermediate point in said source, and a phase-converter having its primary winding connected to said source and having its secondary winding inserted in said connection, whereby an electromotive force is induced 'in said intermediate connection of like frequency to the electromotive force of said source but differing therefrom'in phase.

11. The combination with a source of alternating current, of two alternatin -current motors connected in series re ation across a portion thereof, mechanical coupling means between the rotors of said motors, a connection from a point between said motors and an intermediate point in said source, and a synchronous phase-converter arranged to produce an electromotive force in said connection of like frequency to the electromotiveforoe of the source but differing therefrom in phase and means for varying the amount of d c current excitation of said phase converter, whereby the power factor of the load on said main source may be adjusted.

the commutator type, each of which embodies an armature and a mam field winding, of means for supplying current of dif- I fering phase to'said armatures, a common cross field winding magnetically associated 10 with all of said armatures and exciting means therefor.

In testimony whereof I have hereunto subscribed myname this 29th day of April,

RUDOLF E. HELLMUND. 

